Abstract
Tin (II) sulfide (SnS) is a promising semiconductor material for next‐generation solar energy conversion due to its favorable bandgap, elemental abundance, low toxicity, and low cost. A major challenge, however, lie in the low open circuit voltages that are typically obtained in SnS‐based devices. Herein, a low‐cost solution‐phase deposition technique is used to prepare SnS thin films and investigate different junction materials (Ga2O3 and In2S3) to improve the photovoltage in SnS‐based water splitting photocathodes. Molecular inks are prepared by dissolving SnS powder in solvent mixtures of ethylenediamine and 1,2‐ethanedithiol. SnS thin films are then successfully deposited by spin coating the inks onto substrates, followed by a heat treatment at 350°C in an inert atmosphere. With a photoelectrode based on a SnS/Ga2O3 heterojunction, an onset potential of +0.25 V versus reversible hydrogen electrode (RHE) is achieved for photoelectrochemical hydrogen evolution in pH 7 phosphate buffer, which is until now the earliest onset potential (highest photovoltage) among nontoxic replacements to CdS junctions in SnS‐based water splitting systems.
Highlights
Tin (II) sulfide (SnS) is a promising semiconductor material for next-generation solar energy conversion due to its favorable bandgap, elemental abundance, low toxicity, and low cost
Potential of þ0.25 V versus reversible hydrogen electrode (RHE) is achieved for Various deposition methods have been photoelectrochemical hydrogen evolution in pH 7 phosphate buffer, which is until now the earliest onset potential among nontoxic replacements to CdS junctions in SnS-based water splitting systems
To compete economically with hydrogen produced from fossil fuels, the PEC water splitting devices should be scalable and low cost, which implies the use of earth-abundant, nontoxic, and cheap elements, stability againstcorrosion, and cost-effective fabrication
Summary
The SnS ink was prepared by dissolving a commercial SnS powder directly in a thiol–amine solvent mixture under an inert atmosphere (see experimental section for details). Gallium oxide (Ga2O3) is mainly studied in the transistor field as a wide-bandgap semiconductor material.[26] The ALD grown Ga2O3 is amorphous with a band gap of 5.25 eV,[27] which makes it attractive as a junction layer from a practical perspective as it is transparent, minimizing the loss of light absorption in the underlying SnS layer. >350 mV improvement in the onset potential compared to the SnS/Pt PEC cell This is a further 80 mV photovoltage gain compared to the In2S3 junction layer devices (Figure 4). Surface etching or passivation treatment may reduce the surface defects, which we suspect are one of the major sources of recombination
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